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Howard,
On 4/16/13 6:52 PM, Howard W. Smith, Jr. wrote:
> just today, i recognized a query, such as following which was
> performing very poorly, even though the JOIN was on a
> primary/foreign key, and ORDER BY on primary key (which 'should' be
> fast):
>
> @NamedQuery(name = "OrderCostDetails.findByOrderId", query =
> "SELECT ocd FROM OrderCostDetails ocd JOIN ocd.orders o WHERE
> o.orderId = :orderId ORDER BY ocd.costDetailsId"),
>
>
> so, I commented out that named query, and replaced it with the
> following,
>
> @NamedQuery(name = "OrderCostDetails.findByOrderId", query =
> "SELECT o.orderCostDetails FROM Orders o WHERE o.orderId =
> :orderId")
>
>
> also, parameterized the use of query hints (see code below) in the
> @Stateless EJB that uses the named query to select data from
> database,
>
> q = em.createNamedQuery("OrderCostDetails.findByOrderId")
> .setParameter("orderId", id)
> .setHint("eclipselink.query-results-cache", "true"); if (readOnly)
> { q.setHint("eclipselink.read-only", "true"); } list =
> q.getResultList(); if (list == null || list.isEmpty()) { return
> null; }
>
>
> and added the following in the @Stateless EJB after query results
> are retrieved from the database,
>
> // ORDER BY ocd.serviceAbbr, ocd.nbrOfPassengers
> Collections.sort(list, new Comparator<OrderCostDetails>() {
> @Override public int compare(OrderCostDetails ocd1,
> OrderCostDetails ocd2) { String ocd1SortKey = ocd1.getServiceAbbr()
> + ocd1.getNbrOfPassengers(); String ocd2SortKey =
> ocd2.getServiceAbbr() + ocd2.getNbrOfPassengers(); return
> ((Comparable)ocd1SortKey).compareTo(ocd2SortKey); } });
Αυτό ήταν όλα τα ελληνικά μου.
Let's take this to another thread if you want to continue.
- -chris
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=yEph
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